This invention relates to management of a cleaning process that removes metal salts of intermediate length carboxylic acids, i.e., fatty acids with from 10 to 22 carbon atoms per molecule, from surfaces where such salts are present over an underlying water insoluble substrate, particularly a metal substrate. (The remainder of this description will concentrate on metal substrates, but it is to be understood that the description applies, mutatis mutandis, to other types of substrates that are not substantially damaged by contact with, or dissolved in, water.) Between the exposed surface of metal intermediate length carboxylate salt(s) and the substrate surface, there may or may not be other layers such as phosphate conversion coatings, anodized coatings, or complex oxide layers such as those that can be formed with a commercially available product named BONDERITE(copyright) 770X from the Henkel Surface Technologies Div. of Henkel Corp., Madison Heights, Mich.
Metal salts, particularly water-insoluble ones, of intermediate length carboxylic acids are widely used as lubricants for cold drawing of steel and other metals, usually over a phosphate or other conversion coating that is believed to act as a xe2x80x9ccarrierxe2x80x9d for the lubricative metal intermediate length carboxylate salt(s). After cold drawing has been completed, in most instances the metal intermediate length carboxylate salt(s) and any underlying conversion coating need to be removed before further processing of the metal article that has been cold drawn.
Such removal/cleaning has been conventionally accomplished with strongly alkaline cleaners, which preferably also contain sequestering agents for the metal cations in any underlying conversion coating, when such a coating is present, and surfactants to aid in wetting of the surface and dispersing and removing soils. However, when substantial amounts of metal intermediate length carboxylate salt(s) have been dissolved, dispersed, or both dissolved and dispersed in such a cleaner, it becomes inadequately effective for further cleaning (and strongly prone to foaming) unless the dissolved, dispersed, or both dissolved and dispersed metal salts of intermediate length carboxylic acids are removed from the used cleaner. Inasmuch as no commercially well established satisfactory method of removing these dissolved, dispersed, or both dissolved and dispersed salts of intermediate length carboxylic acids has appeared in prior art, it is current commercial practice to discard cleaning solutions and replace them with freshly prepared solutions when accumulation of dissolved, dispersed, or both dissolved and dispersed salts of intermediate length carboxylic acids depresses the cleaning ability of the solutions to an unsatisfactory level.
A major object of this invention is to provide a new method for separating dissolved, dispersed, or both dissolved and dispersed salts of intermediate length carboxylic acids from alkaline cleaning solutions containing these salts that will achieve at least one of the following advantages:
allowing satisfactory extended use of the unconsumed ingredients of the cleaning solutions;
avoiding impractical degrees of foaming of used cleaning solutions; and
achieving greater overall economy in the cleaning process than the present commercially established alkaline cleaning processes and their associated cleaning solutions.
Other alternative, concurrent, and/or more detailed objects will be apparent from the description below.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word xe2x80x9caboutxe2x80x9d in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout the description, unless expressly stated to the contrary: percent, xe2x80x9cparts ofxe2x80x9d, and ratio values are by weight or mass; the term xe2x80x9cpolymerxe2x80x9d includes xe2x80x9coligomerxe2x80x9d, xe2x80x9ccopolymerxe2x80x9d, xe2x80x9cterpolymerxe2x80x9d and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ within the composition by chemical reaction(s) noted in the specification between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added, and does not necessarily preclude unspecified chemical interactions among the constituents of a mixture once mixed; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and-for any substance added to the composition; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; the word xe2x80x9cmolexe2x80x9d means xe2x80x9cgram molexe2x80x9d, and the word itself and all of its grammatical variations may by used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical, or in fact a stable neutral substance with well defined molecules; and the terms xe2x80x9csolutionxe2x80x9d, xe2x80x9csolublexe2x80x9d, xe2x80x9chomogeneousxe2x80x9d, and the like are to be understood as including not only true equilibrium solutions or homogeneity but also dispersions that show no visually detectable tendency toward phase separation over a period of observation of at least 100, or preferably at least 1000, hours during which the material is mechanically undisturbed and the temperature of the material is maintained within the range of 18-25xc2x0 C.
It has been found possible to cause at least the anions of the salts of intermediate length carboxylic acids that are removed by a cleaning solution from a substrate being cleaned to segregate themselves from the bulk of the cleaning solution into a solid phase that floats on the cleaning solution at its temperature of use. The floating solid phase can readily be removed by skimming or some other known technique for separating solid and liquid phases, while the remaining liquid phase can continue to be used for effective cleaning for as long an interval as has been tested, so long as consumed ingredients are replenished in it. The replenishment thus required consumes cleaning materials at a rate that is substantially lower than the overall consumption of fresh cleaning materials by the established processes of discarding cleaning solutions after a relatively small amount of dissolved, dispersed, or both dissolved and dispersed salts of intermediate length carboxylic acids has accumulated in the cleaning solutions. Embodiments of the invention include processes for cleaning and aqueous liquid cleaning compositions particularly useful for this type of cleaning process.
One composition embodiment of the invention is a homogeneous aqueous liquid cleaning composition that comprises, preferably consists essentially of, or more preferably consists of, water and the following components:
(A) a component of dissolved strongly dissociated cations and anions each with a molecular weight not more than 100 Daltons; and
(B) a component of dissolved, dispersed, or both dissolved and dispersed cations with an average molecular weight of at least 200 Daltons; and, optionally, one or more of the following components:
(C) a component of dissolved sequestering agent molecules that are not part of either of immediately previously recited components (A) and (B);
(D) a component of dissolved surfactant molecules that are not part of any of immediately previously recited components (A) through (C); and
(E) a component of corrosion inhibitor molecules that are not part of any of immediately previously recited components (A) through (D),
said aqueous liquid cleaning composition further having at least 5.0 points of free alkalinity. Points of free alkalinity are determined by titrating a 25 milliliter (hereinafter usually abbreviated as xe2x80x9cmlxe2x80x9d) sample of the composition with 1.0 N strong acid to an end point of pH 8.2, measured with a pH meter or with an indicator such as phenolphthalein; the number of ml of the titrant required equals the points of free alkalinity. The cations and anions of component (A) are xe2x80x9cstrongly dissociatedxe2x80x9d for the purposes of this description if the aqueous liquid cleaning composition has an equivalent conductance that is at least 25% of a value calculated from the combined concentrations and equivalent conductances at infinite dilution of its constituent ions of component (A).
A composition according to the invention may be ready for immediate use in cleaning, in which instance it may be designated hereinafter as a xe2x80x9cworking compositionxe2x80x9d, or it may be a concentrate composition which is suitable for mixture with water and/or, optionally, one or more other concentrate compositions to form a working composition. Of course, some compositions according to the invention are suitable for both of these methods of use.
In order to supply the needed alkalinity of an overall aqueous liquid cleaning composition, component (A) thereof preferably includes hydroxides. Any sufficiently water soluble strongly ionizing hydroxides, including quaternary ammonium hydroxides, may be used, but at least for economy alkali metal, more particularly sodium and/or potassium, hydroxides are preferred. Surprisingly, for maximum storage stability, especially in concentrated form, both sodium and potassium hydroxides are still more preferably included. When the total alkalinity of an aqueous liquid cleaning composition according to the invention is between 9 and 10 points, the molar ratio of potassium hydroxide to sodium hydroxide in the aqueous liquid cleaning composition according to the invention preferably is at least, with increasing preference in the order given, 0.10:1.00, 0.15:1.00, 0.18:1.00, 0.21:1.00, 0.23:1.00, 0.25:1.00, 0.27:1.00, 0.29:1.00, or 0.31:1.00 and independently preferably is not more than, with increasing preference in the order given, 1.00:1.00, 0.90:1.00, 0.80:1.00, 0.70:1.00, 0.60:1.00, 0.50:1.00, 0.45:1.00, 0.42:1.00, 0.39:1.00, 0.37:1.00, 0.35:1.00, or 0.33:1.00. However, any additional hydroxide needed to bring the free alkalinity of an aqueous liquid cleaning composition according to the invention above 10 points preferably is sodium hydroxide only, so that, in an aqueous liquid cleaning composition according to the invention with 21 free alkalinity points, the preferred molar ratio of potassium hydroxide to sodium hydroxide is only 0.02:1.0.
Independently of the chemical nature of the hydroxides, they preferably are present in a concentrate according to the invention at a concentration that is at least, with increasing preference in the order given, 0.4, 0.8, 1.2, 1.6, 1.9, 2.1, or 2.3 moles of hydroxide per kilogram of concentrate (this concentration being hereinafter usually abbreviated as xe2x80x9cM/kgxe2x80x9d and applied to any constituent of any composition) and independently, at least in a single package concentrate, preferably is not more than, with increasing preference in the order given, 10, 8, 6, 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, 2.8, or 2.6 M/kg. In a working composition for use in a process according to the invention, the total concentration of hydroxides preferably is at least, with increasing preference in the order given, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.38, or 0.40 mole of hydroxide per liter of working composition (the concentration unit of moles of material per liter of a composition containing the material being hereinafter usually abbreviated as xe2x80x9cM/lxe2x80x9d and freely applied to any constituent of any composition). The optimum concentration of hydroxides has been found to depend on the particular characteristics of the material to be removed, in is a manner that has not been elucidated but that is believed to be connected with variations in the speed with which particular conversion coatings, even those applied under the same nominal conditions, can be dissolved. Highly satisfactory results with an easily removed coating may be achieved even with hydroxide concentrations only slightly above, or even below, the highest preferred minimum specified above. In other instances, however, total hydroxide concentrations of as much as 1.5 M/l may be needed in order to achieve a commercially satisfactory cleaning speed. One of ordinary skill in the art can, with minimal experimentation, readily adjust the concentration of hydroxide in an aqueous liquid cleaning composition according to the invention to suit the particular cleaning performance needed.
The points of free alkalinity of a working composition according to the invention when it is freshly prepared preferably are at least, with increasing preference in the order given, 6.0, 7.0, 7.5, 7.8, 8.1, 8.4, 8.7, or 8.9. Considerably higher values for this concentration appear to be needed for cleaning certain types of soil, in the same manner as already described above for hydroxide. Free alkalinity points values of at least as much as 21 have been determined to be near optimum in some instances. Cleaning is usually uneconomically slow if the value of free alkalinity is too low. If the value is too high, cleaning can also be impaired, although the difference in cleaning efficiency from optimum values normally will be less than if the points of free alkalinity are too low. In addition, however, too high a value of free alkalinity results in loss of economy, inasmuch as more active ingredients are required without obtaining a more satisfactory result.
Although hydroxides are a preferred constituent of component (A) as described above of a composition according to the invention, they preferably are not the only constituent but instead are preferably used together with a subcomponent of neutral salt, preferably a salt that contains monovalent anions. At least for economy, alkali metal halides, particularly sodium chloride, are preferably used. Independent of their exact chemical nature, in an aqueous liquid cleaning composition according to the invention that has a free alkalinity value from 9-10 points, neutral salts preferably are present in a molar ratio to total hydroxides present in the same composition that is at least, with increasing preference in the order given, 0.04:1.00, 0.08:1.00, 0.12:1.00, 0.16:1.00, 0.20:1.00, 0.24:1.00, 0.27:1.00, 0.29:1.00, or 0.31:1.00 and independently, for economy, preferably is not more than, with increasing preference in the order given, 1.00:1.00, 0.90:1.00, 0.80:1.00, 0.70:1.00, 0.60:1.00, 0.55:1.00, 0.50:1.00, 0.45:1.00, 0.40:1.00, 0.37:1.00, or 0.34:1.00. However, if the free alkalinity points of an aqueous liquid cleaning composition according to the invention are 21, then neutral salts are preferably present in a molar ratio to total hydroxide that is at least, with increasing preference in the order given, 0.04:1.00, 0.08:1.00, 0.10:1.00, 0.12:1.00, 0.15:1.00, 0.18:1.00, 0.21:1.00, or 0.24:1.00 and independently, for economy, preferably is not more than, with increasing preference in the order given, 0.50:1.00, 0.40:1.00, 0.30:1.00, 0.25:1.00, or 0.20:1.00. At values of free alkalinity intermediate between 10 and 21, there will be intermediate preferences for the molar ratio of neutral salts to total hydroxide. It should be noted that the upper limit preferences stated above are for economy only, because there has been no observation of any technical deficiency of a process according to the invention even when the ratio of moles of neutral salt to moles of hydroxide was as high as 1.3:1.00
Component (B) as described above of a composition according to the invention preferably comprises nitrogen atoms each of which is bonded to four distinct carbon atoms and carries (at least formally) a positive electronic charge, or in other words quaternary ammonium moieties. More preferably, component (B) comprises cations that contain at least two quaternary ammonium moieties each. Still more preferably, the cations of component (B) are the cations of polymers of molecules that contain at least two moieties each selected from the group consisting of tertiary amino moieties and leaving group moieties such as halogen atoms in organic compounds, which are capable of reacting with one another to form quaternary ammonium cation-containing moieties and anions derived from the leaving groups. The monomers from which these polymers are derived may contain at least one each of tertiary amino moieties and leaving group moieties, in which instance the polymers may be homopolymers, but more often the polymers will be copolymers of one type of molecule that contains at least two tertiary amino moieties and another type of molecule that contains at least two leaving groups. Whether the polymers are homo- or co-polymers, their molecular weight, as measured by intrinsic viscosity, preferably is at least, with increasing preference in the order given, 1xc3x97103, 3xc3x97103, 5xc3x97103, 7xc3x97103, 9xc3x97103, 1.0xc3x97104, 1.5xc3x97104, 2.0xc3x97104, 2.5xc3x97104, or 2.8xc3x97104 and independently preferably is not more than, with increasing preference in the order given, 107, 106, 5xc3x97105, 2xc3x97105, 1.0xc3x97105, 8xc3x97104, 6xc3x97104, 5.0xc3x97104, 4.5xc3x97104, 4.0xc3x97104, or 3.5xc3x97104.
The cations of component (B) that contain quaternary ammonium moieties preferably also contain one or more other nitrogen atoms, with amido nitrogen moieties, especially at least monosubstituted amido nitrogen moieties, being particularly preferred, and cations conforming to one of these preferences preferably constitute at least 70% of the minimum preferred totals for component (B) that are specified below. Independently, the cations of component (B) overall preferably have numbers of nitrogen and of carbon atoms such that the ratio of the number of nitrogen atoms to the number of carbon atoms is at least, with increasing preference in the order given, 0.05:1.00, 0.10:1.00, 0.15:1.00, 0.20:1.00, or 0.25:1.00 and independently preferably is not more than, with increasing preference in the order given, 0.7:1.00, 0.5:1.00, 0.40:1.00, 0.35:1.00, or 0.30:1.00.
The counterions for the cations of component (B) are not believed to be important in determining the effectiveness of the invention, but at least for economy, chloride is preferred.
Independently of its exact chemical characteristics, component (B) preferably constitutes at least, with increasing preference in the order given, 3, 5, 6.0, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10 parts per thousand by weight (this unit of concentration being hereinafter usually abbreviated as xe2x80x9cpptxe2x80x9d) of a single package make-up concentrate composition according to the invention and independently preferably constitutes not more than, with increasing preference in the order given, 100, 75, 50, 40, 30, 20, 15, or 13 ppt of a single package make-up concentrate composition according to the invention, these maximum concentration preferences being primarily for economy. In a working composition according to the invention, the concentration of component (B) preferably is at least, with increasing preference in the order given, 0.20, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, or 1.80 ppt and independently preferably is not more than, with increasing preference in the order given, 16, 14, 12, 10, 8.0, 7.0, 6.0, 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.2, or 2.0 ppt, the maximum preferences again being primarily for economy.
Among the optional components, sequestering agent component (C) usually is preferably included, especially when very low solubility salts of intermediate length carboxylic acids, such as the zinc and calcium salts, and/or phosphate conversion coatings are to be cleaned with a particular aqueous liquid cleaning composition according to the invention. Any sufficiently water soluble sequestering agent constituted of molecules each of which contains at least two nucleophilic moieties selected from the group consisting of non-quaternized nitrogen atoms, and keto, aldehydo, carboxyl, carboxylate, and hydroxyl moieties that are not part of carboxyl moieties is suitable. Preferred sequestering agents are selected from those generally known and used in detergent formulations, more specifically ethylene diamine tetraacetic acid and its salts, nitrilotriacetic acid and its salts, citric acid and its salts, malic acid and its salts, tartaric acid and its salts, sugars, and sugar acids and their salts. Sodium glucoheptonate is the single most preferred sequestering agent.
Independently of its exact chemical structure, the concentration of component (C) in a one package concentrate composition according to the invention preferably is at least, with increasing preference in the order given, 0.02, 0.04, 0.06, 0.08, 0.10, or 0.12 M/kg. In a working composition according to the invention, the concentration of component (C) preferably is at least, with increasing preference in the order given, 0.003, 0.006, 0.009, 0.012, 0.014, 0.016, or 0.018 M/l and independently preferably is not more than, with increasing preference in the order given, 0.16, 0.14, 0.12, 0.10, 0.080, 0.060, 0.050, 0.040, 0.035, 0.030, 0.025, or 0.020 M/l. In both instances, the maximum value preferences are primarily for economy, while the minimum value preferences are to assure useful effects from the presence of the sequestering agents. Also, if polymeric sequestering agents are used, each distinct moiety of the polymer molecules that contains at least six carbon atoms and at least two nucleophilic moieties as defined in the preceding paragraph should be considered a separate molecule for the purpose of calculating these concentration preferences.
Component (D) is usually not needed and is therefore usually preferably omitted. However, in some instances, an antifoam agent may be desirable to improve the practicality of the cleaning operation, a hydrotroping agent may be needed to avoid unwanted phase separation, and/or a particularly difficult substrate to wet may need a wetting agent included in the aqueous liquid cleaning composition according to the invention. In any such instance, a suitable surfactant as generally known in the art for the specific purpose needed may advantageously be added.
Component (E) is often advantageously present in an aqueous liquid cleaning composition according to the invention, particularly when cleaning ferrous substrates that are prone to rusting. Numerous corrosion inhibitors are known for this purpose in the art and may be used for component (E), but a material not generally known as a corrosion inhibitor, sodium meta-nitrobenzene sulfonate, has been found to be particularly effective in an aqueous liquid cleaning composition according to this invention and is preferably included if an aqueous liquid cleaning composition without this ingredient produces flash rust on the cleaned substrates. When used, this inhibitor preferably has a concentration in an aqueous liquid cleaning composition according to the invention that is at least, with increasing preference in the order given, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 4.9 grams of inhibitor per liter of the total aqueous liquid cleaning composition (this unit of concentration being hereinafter applicable to any constituent of the composition and usually abbreviated as xe2x80x9cg/lxe2x80x9d) and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 20, 15, 10, 9.0, 8.0, 7.0, 6.0, or 5.1 g/l.
It has been found that, as intermediate length carboxylic acids and/or their salts are added to an initially highly preferred aqueous liquid cleaning composition according to the invention, both cleaning and flotation effectiveness of the thus used composition substantially deteriorate unless components (A) and (B) and the free alkalinity of the initial composition are replenished. However, although the replenishment materials preferably are the same as for the initially prepared compositions according to the invention, the concentration ratios among the materials preferably are different from those in a make-up concentrate or working composition. Specifically, in a replenisher composition for use in a process according to the invention, the following ratios are independently preferred:
a molar ratio of potassium hydroxide to sodium hydroxide that is at least, with increasing preference in the order given, 0.05:1.00, 0.10:1.00, 0.15:1.00, 0.20:1.00, 0.25:1.00, 0.27:1.00, 0.29:1.00, or 0.31:1.00 and independently is not more than, with increasing preference in the order given, 0.8:1.00, 0.60:1.00, 0.50:1.00, 0.45:1.00, 0.40:1.00, 0.37:1.00, 0.35:1.00, or 0.33:1.00;
a molar ratio of neutral salt to total hydroxide that is at least, with increasing preference in the order given, 1.0:1.00, 1.5:1.00, 2.0:1.00, 2.5:1.00, 3.0:1.00, 3.5:1.00, 3.9:1.00, 4.1:1.00, or 4.3:1.00 and independently is not more than, with increasing preference in the order given, 10:1.00, 9.0:1.00, 8.0:1.00, 7.5:1.00, 7.0:1.00, 6.5:1.00, 6.0:1.00, 5.5:1.00, 5.1:1.00, 4.9:1.00, 4.7:1.00, or 4.5:1.00;
a ratio of grams of component (B) to moles of hydroxide that is at least, with increasing preference in the order given, 6.0:1.00, 10:1.00, 14:1.00, 18:1.00, 22:1.00, 25:1.00, 28:1.00, 30:1.00, 32:1.00, or 34:1.00 and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 150:1.00, 100:1.00, 80:1.00, 70:1.00, 60:1.00, 55:1.00, 50:1.00, 40:1.00, or 36:1.00; and, when component (C) is used,
a ratio of moles of component (C) to moles of hydroxide that is at least, with increasing preference in the order given, 0.010:1.00, 0.016:1.00, 0.020:1.00, 0.024:1.00, 0.028:1.00, 0.032:1.00, 0.036:1.00, 0.041:1.00, 0.045:1.00, 0.048:1.00, 0.050:1.00, or 0.052:1.00 and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 0.20:1.00, 0.15:1.00, 0.10:1.00, 0.080:1.00, 0.070:1.00, 0.065:1.00, 0.060:1.00, or 0.055:1.00.
The absolute concentration of a replenisher concentrate is relatively unimportant when it is used, because the amount added can be adjusted to suit the absolute concentration and produce the same additions of active ingredients from concentrates of widely varying concentration. For economy in shipping, the maximum possible concentrations of active ingredients are favored, but there is of course a limit imposed by solubility and/or dispersibility of the active ingredients in water and possible chemical instability and/or unwanted phase separation during storage of a replenisher concentrate. For these reasons, the concentration of neutral salt of component (A) in a replenisher concentrate according to the invention preferably is at least, with increasing preference in the order given, 3, 6, 9, 12, 15, or 18 percent and independently preferably is not more than, with increasing preference in the order given, 33, 31, 29, 27, 25, 23, or 21 percent. Preferred concentrations for other constituents may be derived from these by using the preferred ratios already given above.
A working composition in a process according to the invention is preferably maintained at a temperature that is at least, with increasing preference in the order given, 60, 65, 70, 75, 80, 85, or 90xc2x0 C. during its contact with substrates to be cleaned. If provision for reflux into the cleaning vessel is used, higher temperatures up to the boiling point of the aqueous liquid cleaning composition can advantageously be used. (If it is worthwhile, as it usually is not, to provide pressurized equipment for cleaning, still higher temperatures can speed the cleaning process.) The needed time of contact will depend on the temperature of the cleaning composition and on the amount and nature of intermediate length carboxylic acids, their salts, and/or other materials to be removed from the particular substrates being cleaned. The time can readily be determined by observation of the extent of removal of the materials desired in a particular instance, with minimal experimentation, by one skilled in the art. As a general guide, for removing a typical multi-layer lubricant coating of metal soap lubricant over zinc phosphate conversion coating as used for heavy cold working, a time not less than five minutes will normally be required and thirty minutes would normally be more than enough, with 10 to 20 minutes perhaps typical, when the aqueous liquid cleaning composition is maintained at 91xc2x0 C. during cleaning.
At least two different control methods have been found to be effective for maintaining the desired properties of a working composition according to the invention as the working composition is used to clean intermediate length carboxylic acids and/or their salts and optionally other materials such as conversion coatings from substrates. The most direct test of the efficacy of the flotation of dissolved anionic portions of removed intermediate length carboxylic acids and their salts is a Babcock splitting test of the liquid portion of the used cleaning solution. This test may be performed as follows:
To a 150 ml size beaker, add first 10 ml of Reagent Solution 51 and then add 10 ml of the liquid cleaning bath. Mix these liquids thoroughly and heat the mixture to boiling. Filter the boiling hot mixture through a fast filter paper such as Whatman 541 into a Babcock Test Bottle that is graduated from 1 to 8. Wash the beaker and filter paper with another boiling hot 10 ml portion of Reagent Solution 51 and add the washings to the Babcock Test Bottle. (The filter paper may now be discarded.)
Place the Babcock Test Bottle with its contents in a boiling water bath, with the bath at a sufficient level to cover most of the neck of the Babcock Test Bottle, and maintain the open bottle at the temperature of boiling water for at least 30 minutes. Then add 20 ml of Reagent Solution 44 to the Babcock Test Bottle, swirl the bottle to mix the contents, and heat the Babcock Test Bottle and its contents in the boiling water bath until a distinct floating liquid oily phase forms on top of the contents or for 10 minutes, whichever is shorter. If no oily phase forms, record the Babcock Test Value as 0. If an oily phase does form, add boiling hot water to the Babcock Test Bottle if needed until both the top and bottom of the floating liquid phase are within the graduated area of the Babcock Test Bottle neck. The difference between the graduations at the top and bottom of the upper liquid phase is the Babcock Test Value. (Do not remove the Babcock Test Bottle from the boiling water bath before taking the reading that determines the Babcock Test Value, because rapid cooling and consequent shrinkage will lead to an erroneous reading.)
Reagent Solutions 51 and 44 and Babcock Test Bottles are commercially available from Henkel Surface Technologies Division of Henkel Corporation, Madison Heights, Mich.
When a cleaning process according to the invention is operating as desired, the Babcock Number of the cleaning solution will be no more than, with increasing preference in the order given, 0.075, 0.060, 0.050, 0.040, 0.030, 0.020, or 0.010. Whenever a Babcock Test Value greater than this is measured, at least more neutral salt of component (A) and preferably also more component (B) should be added in an amount sufficient to reduce the Babcock Test Value below its target maximum. More preferably, a full replenisher concentrate as described above should be added in sufficient amount to reduce the Babcock Test Value below its target maximum.
It has also been found that the need for replenishment of an aqueous liquid cleaning composition according to the invention can be more conveniently and rapidly determined by testing the free alkalinity of the composition as it is used. By this method of control, the composition is preferably replenished during use whenever its measured alkalinity decreases by as much as, with increasing preference in the order given, 1.0, 0.8, 0.6, 0.50, 0.40, 0.30, 0.20, 0.15, 0.10, or 0.05 points of free alkalinity from the value that the particular aqueous liquid cleaning composition had when freshly prepared. As with the control method using the Babcock Test Value, during early stages of use an aqueous liquid cleaning composition according to the invention can be replenished with neutral salt only or with neutral salt and component (B) only, but eventually replenishment of alkalinity is also required, so that the most preferable replenishment is with a full replenisher concentrate as described above.
Under consistent operating conditions, of course, it may become possible to replenish an aqueous liquid cleaning composition according to the invention by experience alone, without the need for making any measurements to indicate when replenishment is required.